1. Field of the Invention
The present invention relates generally to a power controller for a vehicle. More particularly, the invention relates to a control system for an automotive power source system suitable for controlling an automotive power source having a higher voltage and higher capacity battery than the conventional 14V system, such as 42V system.
2. Description of the Related Art
In recent years, to accommodate the increasing number of electrically actuated on-vehicle devices, such as electrically driven power steering, electrically actuated air conditioner and so forth, and the increasing capacity thereof, it has been proposed to provide a 42V automotive power supply in addition to the convention 14 power supply. In the 42V power supply, since the voltage is three times higher than that of the 14V system, the current can be reduced by one third, reducing power loss and saving on the weight of a harness. Also, adaptation for a large capacity load is facilitated, and the capacity of the battery is larger than that of the conventional battery, and a nickel hydride battery, lithium ion battery and so forth can be applied in place of the conventional lead acid battery for the future. Recently, it has been proposed to provide a system having both a main battery of a 42V system and an auxiliary battery of a 14V system, with both batteries connected through a DC/DC converter for controlling charging from the main battery to the auxiliary battery.
However, in the recently proposed system, the following problem can be encountered. Namely, by utilizing the large capacity of the battery of a 42V. system, it is possible to operate an electrical load, such as an electrically actuated air conditioner, even while the engine is not driven. However, when the remaining capacity of the main battery becomes small, it is impossible to start the engine.
Also, for example, when the lamps are connected to the 14V system, it becomes necessary to turn the lamps ON even when the key switched remains OFF. However, when the capacity of the auxiliary battery is small, remaining capacity is instantly lowered to the lower remaining capacity of the main battery when the lamps are kept ON.
One object of the present invention is to provide a control system for an automotive power supply which can operate an electrical load upon stopping of engine or turning OFF of a key switch, while preventing lowering of the remaining capacity of the main battery.
A second object of the present invention is to provide a control system for an automotive power supply which can operate an electrical load of a low voltage system while a key switch remains OFF, even when the capacity of an auxiliary battery is small.
In order to accomplish the above-mentioned objects, according to one aspect of the present invention, a control system for an automotive power supply having a control portion controlling operation of a power generator and an electrical load mounted on an automotive vehicle, comprises:
remaining capacity measuring means for measuring a remaining capacity of a battery,
the control portion driving a predetermined power load when an engine is stopped or a key switch is held OFF, and operation of the power load being stopped when the remaining capacity of the battery (measured by the remaining capacity measuring means) falls below a predetermined value.
With the construction set forth above, when the engine is stopped or the key switch is OFF, operation of the power load is possible, and lowering of the remaining capacity of the main battery can be prevented.
Preferably, the control portion may set a plurality of threshold values for the remaining capacity corresponding to priority of the power load, to sequentially stop the power load with a low priority, in sequential order according to a reduction of remaining capacity of the battery.
Preferably, the control portion may operate a predetermined power load when the engine is stopped or the key switch is OFF, to start up the engine when the remaining capacity of the battery is lowered below a predetermined value.
Preferably, the control system may comprise another switch for determining whether starting of engine is permitted when the key switch remains OFF. When the key switch is OFF, the control portion may start up the engine only when the other switch is ON.
Preferably, the control system may further comprise means for inputting a remaining amount of fuel information, and the control portion may stop the engine when remaining amount of fuel falls below a predetermined value after starting the engine.
Further preferably, the control portion may stop operation of the power load when the remaining capacity of the battery becomes smaller than a predetermined value, and stops operation of the control system per se.
Preferably, the control portion may resume operation when the key switch is turned ON after once stopping the operation of the control portion per se.
According to another aspect of the present invention, a control system for an automotive power supply having a control portion controlling a power generator or power load mounted on an automotive vehicle, comprises:
remaining capacity measuring means for measuring a remaining capacity of a battery, a main battery, an auxiliary battery and a voltage converter for charging from the main battery via the auxiliary battery,
the control portion operating the voltage converter when engine is stopped or key switch is held OFF, and stopping operation of the voltage converter when remaining capacity of the main battery falls below a predetermined value.